<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>

<div id="container">
    <span v-if="seen">看得见我吗?</span>

</div>

<script src="https://unpkg.com/vue@next"></script>
<script type="text/javascript">

    const demoApp = {
        data() {
            return {
                seen: true
            }
        },
        mounted() {

            setInterval(() => {
                this.seen = !this.seen
            }, 1000)
        }

    }

    Vue.createApp(demoApp).mount('#container')
</script>

</body>
</html>
